In oncology, cancer treatment is often performed using radio frequency (RF) ablation techniques. Conventional ablation techniques use an array of RF needles or tines (“tine array”), which may be configured to deploy in a pre-determined shape or pattern for transferring RF energy into surrounding tissue. For example, in an undeployed state, tines are inserted into a target area while housed within the lumen of a cannula. An undeployed tine array enclosed within a cannula may be placed by inserting the cannula through bone and tissue into a target area. Once inserted, the electrode tine array may be deployed by forcing the electrode tines out of a cannula and into the surrounding target tissue. After deployment, RF energy may be transmitted from the electrode tine array to ablate the target tissue, causing heating and eventual necrosis of cancerous or malignant tissue. RF ablation occurs when a high frequency alternating current flows from one electrode to another, completing a current path, causing ionic agitation. Ionic agitation occurs around an active electrode as a result of frictional heating in the tissue surrounding the electrode tines (e.g., electrodes, RF needle probes, and the like) on an array, leading to cell death and necrosis. After ablating the target tissue, the electrode tine array is then retracted into the cannula.
A need continues for lower profile (smaller gauge) RF probes with larger electrode arrays. In designing for these characteristics, every diminutive amount of space inside the cannula of the RF probe must be utilized. As a result, an electrode array assembly must hold extremely tight clearances and tolerances in concert with the inner diameter of the cannula. Some problems associated with conventional ablation techniques are associated with the deployment of tine arrays. In particular, biological material (e.g., tissue, coagulated blood, and the like) can enter the lumen of a cannula during deployment or retraction. If blood and tissue enters the cannula, mechanical interference (i.e., blockage, jamming, and the like) may result when the electrode tine array is retracted or deployed again. When retracting the electrode tine array, necrosed tissue and blood resulting from the ablation may adhere to the RF needle probes, causing a mechanical interference.
There, thus, remains a need to minimize the entry of biological material into an RF ablation cannula during deployment and/or retraction of electrode tines.